This invention relates to a system for deploying a vertical linear array of sensors (e.g., hydrophones) from a transiting surface or subsurface vessel, and more particularly to a system for deploying an expendable array of sensors.
Hydrophones are widely used for passively localizing sound waves from subsurface targets. A typical hydrophone system consists of a linear array of hydrophones connected to a telemetering unit that is in turn connected by a signal cable to a submarine, or surface ship. Such an array usually consists of a number of hydrophones suspended in a vertical string and spaced in various sections to form high and low frequency arrays of hydrophones. Normally the top of the array is wired directly to the telemetering unit powered by seawater activated batteries. The telemetry unit processes the acoustic array data for transmission to the submarine or surface ship through a cable comprising at least a single insulated conductor.
In other applications, a vertical linear array of thermocouples, or other temperature sensors, may be deployed to determine gradient temperatures of a body of water.
In either the case of localizing sound waves from a target or in determining temperature gradients, the spacing between the elements of the array must be maintained in a vertical line. There is a natural problem in achieving a stable vertical line of sensors due to shear currents and the vertical length of the array. The top of the array will be affected by higher currents than would be the bottom of the array. The result is that the top section tends to tow the bottom section, causing distortion and tilt in the array. However, shorter arrays will naturally be less influenced by shear currents, and an array about 65 feet long will be negligibly influenced (distorted and tilted) by currents. Of greater concern is the influence of the deploying submarine or ship. As it continues to transit, it is essential that the array not be towed. It is also essential that the deploying vessel be free to maneuver or change speed without influencing the array while data signals from the hydrophones are processed and displayed for a required period.